The present disclosure relates to a self-closing device which retracts a unit such as a sheet feeding cassette to an apparatus main body and an image forming apparatus including this self-closing device.
In an image forming apparatus such as a printer or a multifunction peripheral, a sheet feeding cassette in which a sheet to be image-formed is housed is configured to be able to be pulled out with respect to an apparatus main body for replenishment of sheets or the like. In the image forming apparatus, there is provided a self-closing device in which, when the sheet feeding cassette is pushed toward the apparatus main body to a certain extent, the sheet feeding cassette is automatically retracted into a sheet feeding position.
By using the self-closing device, a load required to push the sheet feeding cassette by a user is reduced and thus workability is improved, and the sheet feeding cassette is easily positioned at the sheet feeding position. Also, the self-closing device is provided with a buffering member to buffer a biasing force in a direction in which the paper feeding cassette is retracted.
In a case where a spring is used as a biasing member for retracting the sheet feeding cassette, in respect of the spring characteristics, a difference occurs in biasing force at a time of start of retracting and at a time of completion of the retracting. In general, the biasing force at the time of completion of the retracting is weaker than the biasing force at the time of start of retracting. If the biasing force at the time of completion of the retracting is weak, there may be a case in which a problem occurs in positioning precision of the sheet feeding cassette at the sheet feeding position and thus it is preferable that the biasing force at the time of completion of the retracting be as high as possible. In order to reduce the difference in the biasing force and maintain the biasing force at the time of completion of the retracting, there is a need to increase in size of the spring; and however, in that case, there is a problem that a size of the self-closing device is increased and a degree of freedom in design is reduced.
On the other hand, if the biasing force at the time of completion of the retracting is increased, when a user pulls out the sheet feeding cassette at the time of replenishment of sheets or the like, a large force against this biasing force is required, and workability is impaired. Thus, it is difficult to satisfy both of improvement in the user workability and improvement in positioning precision of the sheet feeding cassette, which are contrary to each other.
As a self-closing device using a member other than a spring as a biasing member, there is proposed a self-closing device which retracts a sheet feeding cassette by using a self-weight of a weight. This self-closing device is constructed such that, when the sheet feeding cassette is pushed up to a predetermined position, the sheet feeding cassette is coupled to the weight and then is retracted to the sheet feeding position by the self-weight of the weight, whereas if the sheet feeding cassette is pulled out to the predetermined position, the coupling to the plumb is released, and thus a load required to pull out is reduced.
However, in the self-closing device which retracts the sheet feeding cassette by the self-weight of the weight, a space housing the weight is required, and the self-closing device becomes heavy by the weight and thus there is a problem that a size of the self-closing device is increased.